Silo type storage tanks are commonly used for containing foodstuffs during processing and/or storage. These tanks can be quite large, ranging from a little over eight feet to a little over twelve feet in diameter in a typical application, and up to a little over sixty feet tall. In order to meet sanitary standards set by a number of regulatory agencies, including 3-A and the USDA, it is necessary that all of their internal surfaces be amenable to being completely cleaned on a periodic basis. One prior art device that has been provided to accomplish this includes a spray nozzle and spray dish located at the top center of the tank, wherein the cleaning fluid sprays through the nozzle and is deflected off the spray dish and against the top and sidewalls to cascade the cleaning fluid down the tank surfaces to thereby clean them. A supply line carries the cleaning solution from the alcove, up the outside of the tank, through the top head, and onto the spray dish. This arrangement requires a ladder, cage, guardrail, and possibly a catwalk to gain access for maintenance and inspection, thus entailing an added layer of expense and inconvenience. In some applications this cleaning apparatus is removable, which then further increases the expense due to the need for ferrules, clamps, and gaskets to accommodate its disassembly/re-assembly. Another attempt in the prior art to address this cleaning problem is shown in U.S. Pat. No. 4,192,332 which discloses a jet spray nozzle located in the lower portion of the tank, extending inwardly from the alcove area. With this device, cleaning fluid is sprayed through spray nozzles at high pressure upwardly against the top and upper sidewalls of the tank so that it may cascade down and clean. This device is similar to a spray ball and requires high pressure and flow rates, all of which again increases the initial cost and on-going operating expense.
These various prior art attempts to solve the cleaning problem all suffer drawbacks which heretofore were unavoidable. They require in some cases significant structural devices (ladders, etc.) which are unsightly, costly, and entail some degree of risk for the workman who must inspect and maintain the cleaning system. Alternately, with the spray ball device, a rather complicated device must be provided which again represents a significant expense, and which itself must be removable from the tank for it to be cleaned and to avoid interference with the operation of the tank. Furthermore, there must be periodic inspection and maintenance. Neither of these approaches allow for the cleaning operation to be conducted automatically and without an operator getting physically involved at some point in time either for operation or maintenance.
In order to solve these and other problems in the prior art, and as disclosed and claimed in the parent cross referenced above, the inventor has succeeded in designing and developing a clean-in-place fixture for a silo type storage tank which is elegantly simple, which eliminates the need for operator intervention, which is self cleaning, which has no special structure requiring expensive manufacture or maintenance, and which effectively cleans all interior surfaces of the tank while remaining fixed in place and without interfering with the operation of the tank. Essentially, the invention disclosed in the parent comprises a channel, duct, tube, or other passageway which is located near the top of the tank and which has an xe2x80x9cangle of attackxe2x80x9d such that a spray emanating therefrom effectively sprays the tank top and virtually the entirety of the tank sidewalls. An overflow tube, which is preferably a vertically oriented standpipe, has its mouth located adjacent the channel outlet so that cleaning fluid overflows out of the tube and against the sidewall just beneath the channel outlet to wash the sidewall beneath it, as well as the outer surfaces of the overflow tube itself. The overflow tube thus cleans that small portion of the tank interior which may be missed by cleaning fluid spraying out of the channel.
The xe2x80x9cangle of attackxe2x80x9d and physical location for the channel may be readily determined in the field for any particular tank size and dimension. However, the inventors have determined that a particular location and xe2x80x9cangle of attackxe2x80x9d works well with a broad range of tank sizes, and thus represents his preferred embodiment as explained below. By xe2x80x9cangle of attackxe2x80x9d is meant that angular orientation of the channel with respect to the interior tank sidewall. The inventors have also determined a channel size as their preferred embodiment which will provide an effective cleaning using the expected flow rates and pressures that have been adopted in the industry. Thus the invention disclosed in the parent is readily adaptable to any existing or new installation without the need for extensive considerations of cleaning fluid pumps or supplies. It has also been determined that these factors are somewhat interrelated such that changing one may be accommodated for by changing another, and yet provide an effective cleaning. Therefore, there is some flexibility in the implementation of the invention disclosed in the parent which will allow for user or designer preference.
Thus, the invention disclosed in the parent represents a significant advance over the prior art by eliminating structural devices, thereby providing an elegantly simpler device at less cost, maintenance, and with greater flexibility in implementation.
As a further improvement over the prior art, the inventors have continued the development of the invention and has found that alternative fixtures are helpful in certain arrangements in efficiently cleaning a tank interior. In one such alternative embodiment, one or more helper tubes may be provided and configured to spray the area of the tank below the main spray opening in place of the overflow tube. These helper tubes may be oriented at any convenient place in the tank, and take any of several different shapes and sizes. For example, the helper tubes may be formed as additional orifices in the tank sidewall or top, such that no xe2x80x9ctubesxe2x80x9d per se are included in the tank. Alternatively, the helper tubes may be actual tubes which extend into the tank and which are directed to the area required to be sprayed. Although the tubes may be located adjacent the spray opening, they may also be located across the tank and at its other side which is the greatest possible distance to be spaced away from the spray opening. These tubes are referred to as helper tubes as they may be somewhat smaller in diameter than the main spray tube. As another variation, a second xe2x80x9cfull sizexe2x80x9d spray tube may be provided and oriented conveniently to divide up the respective areas of the tank between them. They may be positioned to each spray an area that includes the area beneath the other so that additional helper tubes would not be needed. As still another variation, a plurality of xe2x80x9cmainxe2x80x9d spray tubes could be provided, with the tubes being spaced conveniently about the tank to clean an appropriate area. Still another feature that may be included to help disperse the spray is a spike arranged to be in the path of and generally concentric to the spray leaving the spray opening. This spike diverts just enough of the spray to clean the area of the tank below the spray opening. These arrangements can be used in various combinations, the concept being that the clean-in-place function which heretofore was thought of as being only possible with supplemental cleaning and spraying equipment is now for the first time accomplished with permanently installed spray tubes, openings, and diverters that do not interfere with the normal operation of the tank and which eliminate the need for operator access to the tank top or high sidewalls over catwalks and ladders.
In still further development of the present invention, the inventors have discovered that a single spray opening as described above except having a chamfered edge transition and top undercut to the tank sidewall will by itself clean the entire inside surfaces of a tank. This embodiment of the invention eliminates the requirement of any overflow tubes, helper tubes, spikes, etc. It is anticipated by the inventors that the chamfered transition and undercut may have alternate shapes or sizes and yet still be effective in dispersing the spray sufficiently to spray and clean the tank interior. These variations are considered by the inventors to be within the grasp of those of ordinary skill in the art without undue experimentation, given the teaching of the present disclosure. However, explained below is the inventors"" preferred embodiment of a chamfered edge transition and undercut which has been found to achieve a complete cleaning.
While the principal advantages and features of the invention have been briefly explained above, a greater understanding of the invention may be attained by referring to the drawings and description of the preferred embodiment which follow.